Houghton BELAIRE H2000 Owner's Manual page 11

 When you have heard 4 clicks and the end of the duct
is firmly parallel to the top side of the bracket then you
have successfully connected.
Loop
II
Click
Installation of the plenum assembly
 Connect the socket and plug of the display panel wires
and the controller wires; please notice that colors of
the wires should be matching ( yellow to yellow, red
to red, etc ).
These two faces
are parallel
 Attach the plenum assembly to the plenum mounting
bracket by engaging the two parts. You will hear four
clicks to as the parts connect together.
 Fix the plenum assembly on the plenum mounting
bracket with 4 provided pan head screws.
8